/*
 * Copyright 2012, Gregg Tavares.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Gregg Tavares. nor the names of his
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * Various 2d math functions.
 *
 * @module webgl-2d-math
 */
(function(root, factory) {  // eslint-disable-line
    if (typeof define === 'function' && define.amd) {
        // AMD. Register as an anonymous module.
        define([], factory);
    } else {
        // Browser globals
        root.m3 = factory();
    }
}(this, function() {
    "use strict";

    /**
     * An array or typed array with 9 values.
     * @typedef {number[]|TypedArray} Matrix3
     * @memberOf module:webgl-2d-math
     */

    /**
     * Takes two Matrix3s, a and b, and computes the product in the order
     * that pre-composes b with a.  In other words, the matrix returned will
     * @param {module:webgl-2d-math.Matrix3} a A matrix.
     * @param {module:webgl-2d-math.Matrix3} b A matrix.
     * @return {module:webgl-2d-math.Matrix3} the result.
     * @memberOf module:webgl-2d-math
     */
    function multiply(a, b) {
        var a00 = a[0 * 3 + 0];
        var a01 = a[0 * 3 + 1];
        var a02 = a[0 * 3 + 2];
        var a10 = a[1 * 3 + 0];
        var a11 = a[1 * 3 + 1];
        var a12 = a[1 * 3 + 2];
        var a20 = a[2 * 3 + 0];
        var a21 = a[2 * 3 + 1];
        var a22 = a[2 * 3 + 2];
        var b00 = b[0 * 3 + 0];
        var b01 = b[0 * 3 + 1];
        var b02 = b[0 * 3 + 2];
        var b10 = b[1 * 3 + 0];
        var b11 = b[1 * 3 + 1];
        var b12 = b[1 * 3 + 2];
        var b20 = b[2 * 3 + 0];
        var b21 = b[2 * 3 + 1];
        var b22 = b[2 * 3 + 2];

        return [
            b00 * a00 + b01 * a10 + b02 * a20,
            b00 * a01 + b01 * a11 + b02 * a21,
            b00 * a02 + b01 * a12 + b02 * a22,
            b10 * a00 + b11 * a10 + b12 * a20,
            b10 * a01 + b11 * a11 + b12 * a21,
            b10 * a02 + b11 * a12 + b12 * a22,
            b20 * a00 + b21 * a10 + b22 * a20,
            b20 * a01 + b21 * a11 + b22 * a21,
            b20 * a02 + b21 * a12 + b22 * a22,
        ];
    }


    /**
     * Creates a 3x3 identity matrix
     * @return {module:webgl2-2d-math.Matrix3} an identity matrix
     */
    function identity() {
        return [
            1, 0, 0,
            0, 1, 0,
            0, 0, 1,
        ];
    }

    /**
     * Creates a 2D projection matrix
     * @param {number} width width in pixels
     * @param {number} height height in pixels
     * @return {module:webgl-2d-math.Matrix3} a projection matrix that converts from pixels to clipspace with Y = 0 at the top.
     * @memberOf module:webgl-2d-math
     */
    function projection(width, height) {
        // Note: This matrix flips the Y axis so 0 is at the top.
        return [
            2 / width, 0, 0,
            0, -2 / height, 0,
            -1, 1, 1,
        ];
    }

    /**
     * Multiplies by a 2D projection matrix
     * @param {module:webgl-2d-math.Matrix3} the matrix to be multiplied
     * @param {number} width width in pixels
     * @param {number} height height in pixels
     * @return {module:webgl-2d-math.Matrix3} the result
     * @memberOf module:webgl-2d-math
     */
    function project(m, width, height) {
        return multiply(m, projection(width, height));
    }

    /**
     * Creates a 2D translation matrix
     * @param {number} tx amount to translate in x
     * @param {number} ty amount to translate in y
     * @return {module:webgl-2d-math.Matrix3} a translation matrix that translates by tx and ty.
     * @memberOf module:webgl-2d-math
     */
    function translation(tx, ty) {
        return [
            1, 0, 0,
            0, 1, 0,
            tx, ty, 1,
        ];
    }

    /**
     * Multiplies by a 2D translation matrix
     * @param {module:webgl-2d-math.Matrix3} the matrix to be multiplied
     * @param {number} tx amount to translate in x
     * @param {number} ty amount to translate in y
     * @return {module:webgl-2d-math.Matrix3} the result
     * @memberOf module:webgl-2d-math
     */
    function translate(m, tx, ty) {
        return multiply(m, translation(tx, ty));
    }

    /**
     * Creates a 2D rotation matrix
     * @param {number} angleInRadians amount to rotate in radians
     * @return {module:webgl-2d-math.Matrix3} a rotation matrix that rotates by angleInRadians
     * @memberOf module:webgl-2d-math
     */
    function rotation(angleInRadians) {
        var c = Math.cos(angleInRadians);
        var s = Math.sin(angleInRadians);
        return [
            c, -s, 0,
            s, c, 0,
            0, 0, 1,
        ];
    }

    /**
     * Multiplies by a 2D rotation matrix
     * @param {module:webgl-2d-math.Matrix3} the matrix to be multiplied
     * @param {number} angleInRadians amount to rotate in radians
     * @return {module:webgl-2d-math.Matrix3} the result
     * @memberOf module:webgl-2d-math
     */
    function rotate(m, angleInRadians) {
        return multiply(m, rotation(angleInRadians));
    }

    /**
     * Creates a 2D scaling matrix
     * @param {number} sx amount to scale in x
     * @param {number} sy amount to scale in y
     * @return {module:webgl-2d-math.Matrix3} a scale matrix that scales by sx and sy.
     * @memberOf module:webgl-2d-math
     */
    function scaling(sx, sy) {
        return [
            sx, 0, 0,
            0, sy, 0,
            0, 0, 1,
        ];
    }

    /**
     * Multiplies by a 2D scaling matrix
     * @param {module:webgl-2d-math.Matrix3} the matrix to be multiplied
     * @param {number} sx amount to scale in x
     * @param {number} sy amount to scale in y
     * @return {module:webgl-2d-math.Matrix3} the result
     * @memberOf module:webgl-2d-math
     */
    function scale(m, sx, sy) {
        return multiply(m, scaling(sx, sy));
    }

    function dot(x1, y1, x2, y2) {
        return x1 * x2 + y1 * y2;
    }

    function distance(x1, y1, x2, y2) {
        var dx = x1 - x2;
        var dy = y1 - y2;
        return Math.sqrt(dx * dx + dy * dy);
    }

    function normalize(x, y) {
        var l = distance(0, 0, x, y);
        if (l > 0.00001) {
            return [x / l, y / l];
        } else {
            return [0, 0];
        }
    }

    // i = incident
    // n = normal
    function reflect(ix, iy, nx, ny) {
        // I - 2.0 * dot(N, I) * N.
        var d = dot(nx, ny, ix, iy);
        return [
            ix - 2 * d * nx,
            iy - 2 * d * ny,
        ];
    }

    function radToDeg(r) {
        return r * 180 / Math.PI;
    }

    function degToRad(d) {
        return d * Math.PI / 180;
    }

    function transformPoint(m, v) {
        var v0 = v[0];
        var v1 = v[1];
        var d = v0 * m[0 * 3 + 2] + v1 * m[1 * 3 + 2] + m[2 * 3 + 2];
        return [
            (v0 * m[0 * 3 + 0] + v1 * m[1 * 3 + 0] + m[2 * 3 + 0]) / d,
            (v0 * m[0 * 3 + 1] + v1 * m[1 * 3 + 1] + m[2 * 3 + 1]) / d,
        ];
    }

    function inverse(m) {
        var t00 = m[1 * 3 + 1] * m[2 * 3 + 2] - m[1 * 3 + 2] * m[2 * 3 + 1];
        var t10 = m[0 * 3 + 1] * m[2 * 3 + 2] - m[0 * 3 + 2] * m[2 * 3 + 1];
        var t20 = m[0 * 3 + 1] * m[1 * 3 + 2] - m[0 * 3 + 2] * m[1 * 3 + 1];
        var d = 1.0 / (m[0 * 3 + 0] * t00 - m[1 * 3 + 0] * t10 + m[2 * 3 + 0] * t20);
        return [
            d * t00, -d * t10, d * t20,
            -d * (m[1 * 3 + 0] * m[2 * 3 + 2] - m[1 * 3 + 2] * m[2 * 3 + 0]),
            d * (m[0 * 3 + 0] * m[2 * 3 + 2] - m[0 * 3 + 2] * m[2 * 3 + 0]),
            -d * (m[0 * 3 + 0] * m[1 * 3 + 2] - m[0 * 3 + 2] * m[1 * 3 + 0]),
            d * (m[1 * 3 + 0] * m[2 * 3 + 1] - m[1 * 3 + 1] * m[2 * 3 + 0]),
            -d * (m[0 * 3 + 0] * m[2 * 3 + 1] - m[0 * 3 + 1] * m[2 * 3 + 0]),
            d * (m[0 * 3 + 0] * m[1 * 3 + 1] - m[0 * 3 + 1] * m[1 * 3 + 0]),
        ];
    }

    return {
        degToRad: degToRad,
        distance: distance,
        dot: dot,
        identity: identity,
        inverse: inverse,
        multiply: multiply,
        normalize: normalize,
        projection: projection,
        radToDeg: radToDeg,
        reflect: reflect,
        rotation: rotation,
        rotate: rotate,
        scaling: scaling,
        scale: scale,
        transformPoint: transformPoint,
        translation: translation,
        translate: translate,
        project: project,
    };

}));
